GB2428198A - A self-retaining surgical tube - Google Patents

Abstract

A self retaining hollow tube for access into a body cavity which has a folding strut based retention system deployed through the use of two coaxially arranged tubes 14, 15. Preferably outer tube 15 includes one or more struts which may be made of a stiffer plastic material than the tube or may incorporate a stiffening material. The struts may have hinged joints 16, 17, 18 created by an area of weakened or more flexible material. The sections 19, 20 of the struts between the hinged joints 16, 17, 18 may be of equal or unequal length. The outer tube 15 may be split and cut to length after insertion and may include an integrally moulded external plate with a locking mechanism to secure the tube to the exterior body surface. The struts may be covered in a membrane. The inner tube may include a mechanism to deploy the struts.

Description

A Self-Retaining Tube The present invention relates to a self-retaining

access tube used for access to, but not exclusively, hollow viscuses, body cavities and other spaces in the human or animal body. The device finds particular, but not exclusive, use to afford direct access into the body for the instillation of medication or feeding material, or as an access port for possible further procedures or investigations, or as a means to insert further medical equipment for treatment, or to act as a drainage device from within the body to without, for example abscess drainage or urinary bladder drainage.

Using percutaneous access to the stomach as an example of current practice and access tube type: A gastrostomy is a procedure whereby a hollow tube (the gastrostomy tube) is ultimately positioned with one end within the stomach, and the other end being located outside the body, having traversed the abdominal wall.

Gastrostomy tubes are primarily used for the feeding of patients who are not able to take oral feed for whatever medical reason (e.g. following a stroke) . A typical sequence of events culminating in the final placement of the gastrostomy tube is summarised below.

Referring to figure 1, initial puncture is made into the stomach 1 from a point on the skin 2, after the stomach has been inflated with a gas (usually room air) . This puncture is performed with a hollow bore needle 3, of typically one and a half millimetres diameter. Figure 2 shows a guidewire 4 placed through the hollow bore needle which is inserted through the skin such that its end is within the stomach. The wire is therefore located with one end outside the body, passing through the needle such that the other end is located within the stomach.

The needle 3 can then be removed by sliding it off over the wire. This leaves the wire itself partially coiled within the stomach, traversing the stomach wall and overlying tissues, the other end being located outside the body. Using this wire 4 as a guide, the track in the skin and deeper tissues through which the wire passes can then be dilated using one or more dilators 5 (figure 3) which are passed over the wire. These dilators are of progressively increasing sizes and the track is therefore enlarged until it is wide enough to accommodate the requisite sized feeding tube (approximately three to seven millimetres in diameter) Figure 4 demonstrates that once the track is of the required size the gastrostomy tube 6, which commonly has a retaining mechanism, for example a balloon 7, can be inserted. This is often performed through a temporary sheath 8 which can be removed (for example by longitudinal splitting, a type known as a peel-away sheath) . Once the gastrostomy tube 6 is in the correct position (its end within the stomach, the tube extending through the stomach wall, subcutaneous tissues and skin to the outside), the balloon is inflated.

Figure 5 shows a typical gastrostomy device where balloon inflation is achieved by injecting liquid or gas (usually water or air) into an access port 9 which communicates with the balloon 7 (and hence inflates it) via an access channel 10 which is located within one of the walls 11 of the gastrostomy tube.

It is generally accepted by those medical practitioners skilled in the art of gastrostomy insertion that there are several disadvantages to the current design of the gastrostomy tube, which will be illustrated by reference to figure 5: Firstly, the balloon retention device 7 is not very robust and degrades rapidly once inflated. This necessitates gastrostomy tube replacement on a frequent basis (often every few weeks).

Secondly, in order to inflate the balloon it is necessary to have a communicating bore 10 either within one of the walls of the tube 11 or within the main bore of the tube itself 13. This secondary bore 10 is to allow inflation of the balloon and deflation if the tube needs to be removed.

This limits the working diameter of the device bore 13 as the thickness of the wall 11 needs to accommodate the necessary bore 10 (as the overall diameter of the device is generally constant). This is illustrated by the necessary increase in the thickness of the wall with the bore 11 compared to the wall without a secondary bore 12.

This is a major disadvantage particularly in newer generation small bore tubes such as 12 French size (3-4 millimetre device diameters) Thirdly, the communicating bore 10 by necessity has a valve 9 on the extracorporeal portion such that when fluid is introduced to inflate the balloon it remains in the balloon and does not leak out. The addition of this valve and bore increases the complexity of the device design, complicate device manufacture and are potential sites of device failure.

Fourthly, the necessary integrity of the aforementioned valve 9, balloon 7 and communicating bore 10 such that there is no leak from the retaining mechanism means that the tube length cannot be altered (for example by being cut to a shorter length) once it is inserted into the stomach. An inability to shorten the tube results in more of the device protruding from the skin's surface than is ideal, resulting in a larger focus for infection, decreased patient comfort and poor cosmetic result.

To overcome these problems, the present invention proposes replacing the balloon with a single strut or plurality of struts that may be folded outwards once the device is in position within the stomach. For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying illustrative drawings in which the device and its use is described: The device (figure 6) consists of two coaxial plastic tubes, the inner tube 14 sliding within the outer tube 15.

One end of each strut is attached to the innermost tube with a flexible joint 16. This joint 16 is illustrated as being at the very tip of the innermost tube, but it may be at any position along the innermost tube. The strut has a second flexible joint 17 at some distance along its length. The final end of the strut is attached to the outermost tube, again with a flexible joint 18. The skilled reader will appreciate that traction on the external end of the inner tube will result in shortening of the distance between the joint 16 and joint 18 of each strut. Figure 7 shows the resultant folding out of the struts as the distance between the joints 16 and 18 is reduced. The struts begin to deploy by bending at the hinged attachments to the innermost tube 16 and outermost tube 18, and at the central flexible joint 17. By then fixing the position of the innermost and outermost tubes relative to one another the strut or struts can be maintained in this deployed position.

The two tubes can be manufactured of very thin materials (typically plastics) and as such the overall dimensions of the combined wall may be substantially reduced when compared with the thickness required in a conventional device, as a balloon inflation channel is not required.

As illustrated in figure 7, each strut is composed of five main components, the flexible hinged attachments to the inner tube 16 and outer tubes 18, and a further hinge 17 along the length of the strut. The flexibility in the strut that creates these hinges may be achieved through the use of a flexible plastics material which may or may not be the same material from which the tube is manufactured. Alternatively the hinge may be created by localised removal of some of the strut material (e.g. by grooving or hole cutting) at the site on the strut where the hinge is required. The joint 17 rather than being composed of a short hinge point, may be composed of a longer length of relatively more flexible material allowing progressive bending to occur along the length of this segment. This will result in a more rounded contour to this hinge.

The sections 19 and 20 of the strut/struts between the joints are manufactured from a semi-rigid material of, for example but not exclusively, plastic, or plastic impregnated with a more rigid material such as a metal or metal alloy.

The lengths of the two semi-rigid inter-joint regions of the strut/struts 19 and 20 may be varied at manufacture such that they may be equal or unequal in length. Section may be longer or shorter than section 19. In addition, the distance that the inner tube is retracted and hence the effective shortening of the distance between joints 16 and 18 within the body may also be varied. This variation in the distance between the hinge points may be achieved by the end user (being dependant on how far the inner tube is retracted) or by the amount of shortening that is allowed by the device itself (determined during manufacture). The combined effect of varying the section lengths 19 and 20, and the effective shortening of the distance between the hinge points 16 and 18, is to vary the angle 21 made by the section of the strut 20 to the long axis of the catheter when the strut/struts are deployed. This angle 21 may be any suitable angle, below, equal to or even greater than ninety degrees.

One of the problems with traditional gastrostomy devices is that it is not possible to cut them to a desired length. This device overcomes this problem: Figure 8 illustrates the device once it has been inserted and the struts have been deployed. The outer catheter can be secured by clip mechanism 22 at the skin surface. The outer tube is manufactured in such a way that it is of the peel-away type and can be peeled back to the level of the clip. Once this has been achieved the peeled segment of outer catheter can be cut, leaving the exposed inner tube that can also be cut if required and then anchored to a fixation device on the skin surface or attached directly to an injection port or hub.

The skilled reader will have ascertained that for the device to function well, the outer tube needs a certain rigidity to resist collapse during the withdrawal of the inner tube and strut deployment. The inner tube can be made of any suitable flexible material. Once the struts are deployed and the outer tube cut down to the clip mechanism 22 the inner tube 14 may be cut to the desired length and a hub attached. Alternatively the inner tube can be coiled or simply laid flat against the skin.

Once a gastrostomy device has been in-situ for several weeks a track develops through which a tube can easily be reinserted should the gastrostomy tube need to be replaced. In these situations the exact length of the tube needed can be ascertained from gradations that are located on the inner tube showing the distance from the end of the device within the body to the visible inner tube outside of the body. A device which has been manufactured to the requisite length can then be inserted.

This device (figure 9) differs from the device that can be shortened by cutting in that the outer tube is not of the peel-away type. The outer tube is attached to plate 23 which sits flush against the skin surface. This plate has a retention mechanism for example a curved block 24 over which the inner tube can be pulled and a suitable locking mechanism, for example retaining recess 25 into which it can be inserted and secured in place.

In some instances there may be a concern that there is leakage back along the tube track from the stomach. In these cases is would be possible to have a plastic membrane 26 (figure 10) attached to the device struts.

When the struts are deployed the membrane is unfolded which helps create a seal against the stomach wall to stop such leakage.

Note that a potential space 27 (figure 11)exists between the inner tube and the outer tube. It may be possible for fluid to leak into this space. This is reduced by having a very close fit to the two tubes, and also incorporating a bump stop 28 attached to the innermost tube so that when deployed the stop will abut the outer tube and close off this potential space. This bump stop may also incorporate a locking mechanism to further lock the struts once deployed.

Figure 12 demonstrates a further embodiment of the device whereby the inner tube terminates at a shorter length than previously described and is connected to a thread 29, or wire or other pulling device that is used to apply traction to the inner tube to deploy the struts.

The above features when combined provide a retaining catheter mechanism of which there are two preferred embodiments: A primary gastrostomy tube device that may be cut to the desired length which would be used for initial insertion.

A secondary gastrostomy tube device to be used for tube replacement once a mature track has developed. This would consist of a range of devices manufactured to different lengths and used according to the requirements of the patient. The features of importance for both device embodiments are: A hinged semi-rigid strut/struts based retention device.

This is more robust and less complex in its design compared to conventional balloon systems, reducing the need to change the device so frequently and reducing the number of sites of infection and likelihood of device failure.

A device which can be cut to the desired length during or following insertion resulting in a shorter length of protruding tube affording a greater degree of comfort, a reduced risk of infection and a reduced risk of accidentally pulling the device out.

Devices that may be manufactured to a much smaller diameter with increased central bore to device thickness ratio.

Of course the device may be inserted over a guide wire as current devices can, and can be easily removed at a later date for replacement should this become necessary.

Removal is simply achieved by unlocking the inner tube from its retaining device and pushing the inner tube forward into the outer tube. This will retract the struts allowing them to lie flat against the inner tube affording easy device removal.

As discussed the current invention pertains not only to gastrostomy tubes, but also to tubes inserted into what are termed virtual spaces, for example but not exclusively, the pleural space for pleural fluid drainage or peritoneal space for ascites drainage as well as hollow viscuses such as the bladder. The device may also be inserted into abscesses within the body for drainage.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification, in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features

disclosed in this specification (including any

accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims (14)

1. A self retaining hollow tube for access into the human or animal body, which has a folding strut based retention system deployed through the use of two coaxially arranged tubes.

2. A device as claimed in 1 where the number of struts for retaining the tube may be one or a plurality of retaining struts of any number.

3. A device as claimed in 1 or any preceding claim in which the struts are made more stiff than the remainder of the outer tube by manufacturing them from a stiffer plastics material.

4. A device as claimed in 1 or any preceding claim in which the struts are made more stiff than the remainder of the outer tube by the incorporation of a stiffening material such as a wire, metal or metal alloy.

5. A device as claimed in 1 or any preceding claim in which the hinged joints of the struts are created by weakening of the strut at the joint site by localised removal such as grooving or hole cutting of the strut material.

6. A device as claimed in 1 or any preceding claim in which the hinged joints of the struts are created by their manufacture from a material more flexible than the strut section material itself.

7. A device as claimed in 1 or any preceding claim where the lengths of the rigid or semi-rigid strut sections may be equal.

8. A device as claimed in 1 or any preceding claim where the lengths of the rigid or semi-rigid strut sections may be unequal.

9. A device as claimed in 1 or any preceding claim where once the struts are deployed the angle between the strut sections and the longitudinal axis of the device may be of any angle between one degree and 180 degrees inclusive.

10. A device as claimed in 1 and any preceding claim where some or all of the outer tube may be longitudinally, axially (or a combination of both) split and as such can be cut to the desired length after insertion.

11. A device as claimed in 1 and any preceding claim where the outer sleeve may be integrally moulded with an external plate that can lie flat against the body.

12. A device as claimed in 1 and any preceding claim where the external plate is combined with a locking mechanism to secure the inner tube in a locked position.

13. A device as claimed in 1 or any preceding claim whereby the struts may be partially or completely covered in a membrane.

14. A device as claimed in 1 or any preceding claim where the inner catheter is wholly or partially replaced along its length with a thread, wire or other mechanism to apply traction on the inner tube and deploy the struts.